First, the ability to frame later by cropping. And this, in turn, often means that a single prime can work for many situations you wouldn't otherwise consider using it for. And that means that you can use a fast lens where otherwise you might not have been able to.

More pixels also mean, when one has shot a crowd or something complex such as a ship's rigging or a beaded dress, that one can access that detail for any reason from historical to familial purposes.

More pixels mean that on those occasions when editing is required, flaws tend to have higher pixel count regions that distinguish those flaws from the surrounding image data, and when that is so, it is easier to remove moles, zits, flies, and so forth.

More pixels mean that astro shots, or really shots of anything at a distance you cannot significantly close, contain more usable detail. In the case of astro, some DSOs are so small that the detail gained by a high pixel density sensor is a significant portion of the entire value of the shot.

More pixels mean that not only can you crop for framing, you can also crop in an arbitrary, artful manner - pull a panoramic crop out of a standard ratio lens shot, for instance. Or a vertical slice containing only one skyscraper.

So while yes, certainly you can get great images with just a few MP, not all doors are open, or as open, as they are when you have a higher density sensor.